Had a really weird issue on Friday. Comcast internet goes down for scheduled maintenance @ 2am. Was supposed to be restored at 6am. When i got up around 7am still had no internet. Comcast has done these maintenance outages before and my router never had an issue with it.
Logged into router and discovered the router was trying to connect to comcast modem. status symbol was just spinning. Rebooted modem, got a LAN IP in the modem’s subnet (192.168.100.x) which is normal on boot up, but never got a public IP address.
WTH This router has been working fine since 2020…
So i reached out to comcast and they did not detect any issues.
I plugged in my laptop direct to the modem and got an IP address. Ok WTH again
So i reboot the modem, reconnected router, still no internet.
At this point, I thought my modem may have been having issues (there is a speed issue which is related to the service drop on my house). So i bought a new modem (needed newer one anyways). Installed it and no changes with the router. I then try updating the firmware. Still no internet
At this point, issue is now pointing towards the router (that has been working fine since 2020). So i downloaded the config, and installed a backup balance 20x router I have. I factory reset it and voila internet works. Ok so then i load the config from my other router. It reboots and no internet. Ok this is really weird. So i try updating firmware to 8.5 on the backup router, still no internet. Reset back to factory and internet works.
What am I missing here?
I am gonna load the config on the backup router, and rebuild my production router step by step to see if i can find any setting that breaks the connectivity.
It was painful to read this. Peplink routers, in the past, have had problems connecting to cable modems. At one point the problem was solved with a generic consumer router connecting to the modem and the Peplink router connecting behind it.
While the normal sequence of events is to power on the modem, wait a minute and then power on the router, when that fails, try the reverse sequence. But start with both powered off.
Peplink got me squared away on my support ticket. they suspect that the MAC cloning on WAN port that ive had in place since I discovered the “LAN MAC being used for WAN MAC” bug many years ago, along with auto MTU (Comcast claims they use 1500 and auto should be fine) were the culprits.
I turned MAC cloning off and set MTU to 1440 and voila. very odd since ive been using those settings for years now without issue on the same 20x…
The issue with Comcast modems usually stems from the modem locking on the first MAC it sees. It will then ignore any other traffic from any other MAC address. In the past there was a bug (see: Surf soho mk3 never finishes connecting to cable modem if modem reboots) that was resolved that leaked certain LAN ARP packets onto the WAN port under certain conditions. That resulted in the modem locking onto a MAC address that was not the one of the router WAN port and thus it was ignoring the WAN port talking to it later on. This caused the peplink router to stay in the “connecting…” phase forever. Even though the bug was resolved, I still see some LAN packets leaking to the WAN during the router boot up (Balance 20x, and SOHO) on some rare occasions, causing that connecting bug to happen.
So, in your case, I suspect the MAC cloning feature activates at some point during the boot. So it is possible based on timing, that in some cases, the modem sees the true MAC of the WAN port first, and then when cloning enables itself, the modem refuses to talk to the router which now has a different MAC. Removing cloning solves this case as you saw, because the router does not change MAC address during the boot sequence.
In general, the solution when this happens is just to restart the modem.
Hope this helps.
yeah i actually stumbled on that issue many years later when my balance 20x was having the same problem. Peplink had to release another fix for it in a subsequent firmware update. I guess it wasnt fixed the first time